Wavetek 147 Especificações descarregar pdf (Página 150)

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Measuring System Performance: Modulation Measurements

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The MODULATION screen allows you to monitor the video depth of

modulation in graphical and precise numerical format. The software shows a

marker at the optimal modulation level (NTSC 87.5%, PAL 90%) to assist

you in making adjustments. You can also listen to the audio modulation of

the tuned channel or frequency.

Fig. 6-8 shows the screen for Video Depth of Modulation, which is the ratio

of peak downward change in modulation to carrier amplitude, expressed as

a percentage.

To measure modulation, use the Navigator menu or press the MOD

measurement mode key.

Fig. 6-9 shows the Video screen. Notice the index arrow on the

left side of the vertical bar graph—(87.5%)—indicates the Video

icon is active.

Fig. 6-9 The MODULATION Video Screen

In the event of weak or bad signal, the screen displays:

ERROR

INSUFFICIENT SIGNAL LEVEL TO

PERFORM THE MEASUREMENT

Pressing the Audio soft key activates the screen shown in Fig.

6-10. A built-in 13 dB amplifier and/or 50 MHz low-pass filter

can also be activated.

MODULATION MEASUREMENTS

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